Accessibility - Option to bold mistakes (for greyscale)

[quasijem]

I've recently started using my phone in greyscale mode, and I've found several of the puzzles are harder to read and notice mistakes in when this is turned on. This is mostly a problem with games that have numbers or lines in them, as the thin red is rendered as a hard-to-see dark grey.

I was hoping for an option in display settings to draw mistakes (at least for lines/numbers) in bold. This could also apply to other highlighting, such as in Dominosia.
Alternatively, there could be an option for the red to be a slightly lighter shade, as it is in Bridges; outlines for the number boxes, as in Range; or highlighting the background of the number, as in Train Tracks.
Changing the colour seems necessary for red errors shown against a black background, such as in Mosaic and Unruly, and for the dark-red duplicate dominoes in Dominosia.

I think that the other places errors are shown are clear enough:

• errors in Unequal/Adjacent for arrows/adjacency, in Train Tracks for loops and unconnected pieces, and in Filling for a too-large region are different enough shades that they're easily distinguishable
• that the background is highlighted in Galaxies and Rectangles when the created region is valid makes finding errors easy
• errors at black dots in Pearl make the dot appear bigger and more visible

I've attached a screenshot of several greyscale-rendered puzzles, all containing errors of which most are difficult to read: